This invention relates to a system for locking the blades in position on the stator case of an axial compressor.
Stator cases for axial compressors are formed either as a single piece or in two semi-cylindrical pieces which are then connected together after being provided with the respective blades. In both cases, the blades are mounted by adjacently inserting their bases or feet into suitable circumferential dovetail guides or housings provided on the inner surfaces of said stator cases. This insertion is done from the outside in the case of closed stator cases or laterally in the case of two-piece stator cases until said guides are completely filled. Systems already exist for locking the blades in position on the stator case of an axial compressor. In one of these known systems, specifically applied to closed stator cases, the blades inserted in the circumferential guides are locked in position by a single elastic band or other complicated locking means which, acting from the outside of the stator case, press simultaneously on the backs of the feet of all the blades to push said feet against the edges of the circumferential guides. In addition to increasing the radial dimension of the compressor, this system has the disadvantage that the blades are not all subjected to the same locking load because of inevitable constructional imperfections in the blade feet, so that the elastic band does not press uniformly on the backs of the feet.
In another known system, applied specifically to two-piece stator cases, the blade feet are constructed accurately with the same dimensions as the cross-section of the circumferential guide, so that they perfectly fit into the corresponding guide where they remain spontaneously locked in position. Such a system not only does not change the radial dimension of the compressor, but by reducing the gap between the guide and blade to practically zero ensures that all the blades are in an identical condition and operate under identical conditions. However, this system has two disadvantages. First, a complicated construction is required for accurate sizing of the guides and blade feet. Second, the impossibility of using a compressor with this blade locking system for compressing substances which in time are able to form dust deposits, such as uranium hexafluoride in radioactive uranium enrichment processes. In this respect, dust deposits create incrustations between the blade feet and the respective guides which lock them rigidly together, so making rapid dismantling of the blades impossible in the case of damage or for cleaning purposes.